In a conventional in-cylinder gasoline injection type internal combustion engine provided with multi-hole injector, for example in Japanese Patent Laid-Open Publication No. 2005-139989, it is proposed that nozzle holes in the injector vary in radius of a curved surface of each nozzle hole's inlet portion so that penetrations of fuel sprays from the nozzle holes vary in penetration.
For an in-cylinder gasoline injection type internal combustion engine, it may be required to carry out an ignition retard combustion method wherein ignition timing is made later than a top dead center in a fast idle condition at the time of starting in a cold state to lower combustion efficiency intentionally and raise an exhaust gas temperature. In the ignition retard combustion, it is necessary to concentrate an air-fuel mixture around a spark plug in order to ensure stable combustion, and a fuel spray injected from each nozzle hole is supplied into the associated cylinder by means of an injector which is directed to the vicinity of the spark plug or to a specific lower position. After warming-up the engine, however, it is intended to effect complete combustion and attain both engine emissions cleaning and improvement of output by homogeneous combustion superior in combustion efficiency. To this end, it is necessary that fuel is injected into the cylinder at the intake stroke to form a homogeneous air-fuel mixture. However, since in-cylinder pressure of the intake stroke is equal to the atmospheric pressure or lower than the atmospheric pressure, a penetration of the fuel spray injected in the intake stroke becomes long and the fuel spray is apt to adhere to the cylinder liner. Besides, the cylinder liner may become worn due to the dilution of oil. Further, smoke may occur in the cylinder due to the adhesion of fuel to the cylinder and piston, consequently deterioration of engine emissions and vaporization of fuel may occur, and may result in lowering of output of the engine.
For solving such a problem it is necessary that the penetration of a fuel spray injected from the nozzle hole directed to the spark plug should be made small. According to the above mentioned conventional prior art in which nozzle holes vary in radius of the curved surface of each nozzle hole's inlet portion, penetrations of fuel sprays from the nozzle holes can vary in penetration. However, the curved surface radius of the nozzle hole's inlet requires a high machining accuracy because the size of the nozzle hole is very small. Besides, the required amount of fuel and the actual amount thereof may be different from each other under the influence of a machining error and thus mass production is difficult. Another method is to vary in nozzle hole-diameter. However, the larger the nozzle hole-diameter, the more a particle diameter of the fuel spray may become large and the combustion performance may be lowered.
The present invention is to provide an injector capable of making the penetration of a fuel spray directed to a spark plug small without any special machining and capable of improving both combustion in a cold state and combustion after warm-up of the engine, as well as an in-cylinder gasoline injection type internal combustion engine using the injector and a method for controlling the engine.